Type: Weapon Group
Source: Unearthed Arcana
You understand how to use the exotic double weapons associated with the weapon groups that you have mastered.
Prerequisite: Base attack bonus +1
Benefit: Whenever you take a Weapon Group proficiency feat, you also gain proficiency in the exotic double weapons associated with that group. When you take this feat, you gain proficiency in the exotic double weapons associated with the weapon groups that you already know how to use.
Some exotic double weapons require you to be proficient with two weapon groups to gain proficiency in their use from this feat.
Axes: orc double axe, dwarven urgrosh (must also have Weapon Group (spears and lances)).
Flails and Chains: dire flail, gyrspike (must also have Weapon Group (heavy blades)).
Heavy Blades: double scimitar, gyrspike (must also have Weapon Group (flails and chains)), two-bladed sword.
Maces and Clubs: double mace.
Picks and Hammers: double hammer, gnome hooked hammer.
Spears and Lances: dwarven urgrosh (must also have Weapon Group (axes)).
Special: If you include exotic double weapons, the DM should assign those weapons to a weapon group as appropriate for the campaign.
Normal: When using a weapon with which you are not proficient, you take a -4 penalty on attack tolls.